Health indices were generally flat Monday, but biotech stocks faced turbulence as takeover talk, study results, product problems and regulatory actions sent certain names all over the map.

Investors pumped Biogen Idec ( BIIB) 18.8% to $82.51 Monday after the company announced post-close Friday that third parties -- including famed investor Carl Icahn -- had expressed interest in acquiring the company . Icahn reportedly made a $23 billion bid for the company.

Biogen's Tysabri partner Elan ( ELN) gained ground Monday as well. The company, which has a 50% interest in the MS drug (which is also being reviewed for Crohn's disease), hired Lehman Brothers to advise on its options if Biogen is acquired by a third party. Elan said that under the terms of its agreement, it can acquire for fair value Biogen's 50% economic interest, sell its 50% interest, continue with the existing agreement or restructure the agreement in conjunction with a potential acquisition.

Elan rose $1.82, or 8%, to $24.17. Also, as if there weren't news enough, Biogen and Elan also said Monday that the Food and Drug Administration will take an additional three months to review Tysabri for use as a Crohn's disease treatment.

Speaking of regulatory action, Telik ( TELK) added 48 cents, or 13.9%, to $3.94 after announcing that the FDA lifted a partial hold on Telcyta clinical trials, permitting the company to resume clinical development of the cancer drug.

If you liked this article you might like

Stocks Mixed After Working on Railroad

Stocks Mixed After Working on Railroad

Stocks Log a Volatile Win

Stocks Log a Volatile Win

Stocks Get Spooked

Stocks Get Spooked

Dow's Gain: 199.89 as GDP Wows Wall Street

Dow's Gain: 199.89 as GDP Wows Wall Street

Stocks Trip Over Charts; Nasdaq Pummeled

Stocks Trip Over Charts; Nasdaq Pummeled